<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>React</title>
  </head>
  <body>
    <script>
      (function() {
        function refreshRem() {
          document.documentElement.style.fontSize =
            (document.documentElement.clientWidth / 750) * 100 + 'px';
        }
        refreshRem();
        window.addEventListener('resize', refreshRem);
      })();
    </script>
    <div id="root"></div>
  </body>
</html>
